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KEF LS50 Bookshelf Loudspeaker Review

by admin on August 11, 2014

Even before you hear KEF’s new LS50 speaker, there’s no doubt it’s a unique design. At a glance, this two-way bass-reflex compact looks like little more than a stout box-speaker from an indeterminate era—as simple as it gets.Designed to celebrate KEF’s 50th anniversary, it tips its hat to the BBC monitors of the 70s. It bears zero resemblance inside or out to the birch-ply two-ways of that era—popularized by Spendor, Rogers, Harbeth, and, of course, KEF.

The speaker stands 11.9 inches tall, 7.9 inches wide, 10.9 inches deep, and weighs 15.8 pounds. The MDF cabinet has the build quality of a very high-end design. The sound is just as extraordinary as the look, and the LS50 can be used as a desktop monitor or as hi-fi speakers.
The LS50’s proprietary driver combines a ribbed 5.25-inch aluminum/magnesium woofer with a 1-inch aluminum dome tweeter, the driver sports a die-cast aluminum frame, and the tweeter has that nifty-looking Tangerine waveguide that uses “radial air channels to produce spherical waves up to the highest frequencies.” The LS50’s curved front panel is made of a polyester resin combined with glass fiber and calcium carbonate. The speaker’s rear hosts heavy-duty binding posts that match the quality feel of the rest of the speaker. There are no provisions for wall mounts or brackets, but this isn’t really the sort of speaker that sounds best hugging a wall.

Despite the LS50’s obvious physical differences from the Blade, these speakers have much in common. KEF has applied many of the same engineering principles for coincident-driver technology, internal damping, and innovative baffle design. The unique curvature and composition of the baffle is directly related to the Blade project and is designed to mitigate diffraction effects and spurious reflections—keys to good soundstaging and imaging. The elliptical reflex port is offset in an upper corner of the rear panel. Its profile reduces high-level turbulence—sources of compression and distortion. The ribbing associated with the Z-Flex surround ensures that the surround does not cause any excessive discontinuity for sounds radiated from the high- frequency driver.

The enclosure, including baffle, is as non-resonant as I’ve experienced at this level. Cabinet construction is all MDF, but KEF analysis has optimized placement of the internal bracing. Add to that the constrained-layer damping placed between the internal bracing struts and the inner walls of the cabinet, and the term “acoustically dead” has rarely been more applicable.

When sizing up the potential of a coincident-driver eleven- inch cube like the LS50, one might assume that it would likely be a “voice” speaker—something more akin to a bridge monitor with distinct, perhaps even serious, wideband limitations. But this isn’t the case. Even under levels of dynamic stress that would send a lot of other mini-monitors heading for the hills, the LS50’s output is remarkably even. It hardly flinches, even when it’s pushed hard. This is impressive, but high output alone is not much of a trick for small speakers nowadays. What is much rarer is high output with linearity and extension.

Summing Up

Which speaker you will prefer will depend very much on your tastes in sound and music. Classical orchestral, solo piano, and vocal recordings were better suited to the more neutrally balanced KEF, and rock to the B&W, with its more laid-back low treble and more extended low frequencies.
For KEF’s LS50 Anniversary Model to do so for a penny under $1500/pair makes it even more remarkable. the LS50s do their job with hardly anything being lost in translation. They’re superb all rounders, comfortable with a wide genres of music and create equal impact played soft or loud.